Plot of the Gaussian area, in units of km s⁻¹ × normalised flux units, of the blue-shifted absorption feature divided by that of the red-shifted feature for combination profiles. Combination profiles in Lupus are denoted by circle markers, and those in Upper Sco are marked by an X. The horizontal dashed line (where the ratio is equal to 1) marks where the area of the blue and red features are equal. Blue or red coloured markers indicate blue- or red-dominated sources.